A Multi-Functional Organic Charge Coupled Device

The charge injection device (CID) and the charge coupled device (CCD) fabricated on silicon have a wide range of applications, the most common being in image capture for example in digital cameras and sensitive image arrays in astronomy. These devices are composed of arrays of two-layer capacitors fabricated adjacent to each other. One layer is a semiconductor, the other an insulator. In these devices charges are induced at the semiconductor/interface either electrically or optically. By applying suitable voltages across successive capacitors these charges can be moved through the array from one capacitor to the next. The CID is composed simply of two capacitors but is extremely useful for studying the generation and transfer efficiency of charges from one capacitor to the other. The CCD is a multicapacitor array. Until our recent publication of an organic CID no laboratories had previously reported organic versions of these two devices. This project is directed at demonstrating a multi-functional organic charge coupled device (CCD). Initially the programme will characterise fully our groundbreaking demonstration of an organic CID which is, in essence, a single-stage CCD. We plan to utilise the optical response of the CID to investigate the interface physics of the device. We will study specifically chosen insulator/semiconductor combinations in order to obtain the essential information on the dynamics of charge transport and trapping at the insulator/semiconductor interface. This information will allow us to design and fabricate the optimum test structure and identify the appropriate test conditions for demonstrating a multi-functional organic CCD. The device offers opportunities for exploitation in signal processing and imaging applications that are compatible with printed plastic electronic systems, a key investment area for the UK Government.

Plastic Electronics is already realising its potential for applications in ultra-thin displays and is showing great promise in a wide range of other applications such as solar panels, intelligent packaging and printable logic. In 2010, the value of the market was ~$1.8 billion dollars and was predicted to rise to $5 billion by 2012 (IDTechEx). The UK Government has recognised Printed Electronics as a key growth sector for the UK. Building on the sector's world leading research supported for decades by EPSRC, initially through initiatives on Electroactive Materials and Carbon-based Electronics, there has been significant recent further investment; >£50M in a state-of-the art National Centre for Printed Electronics (PETEC) in Sedgefield and on-going support through TSB, KTP and IeMRC funding for collaborative research and technology transfer projects. As an Emerging Industry, Plastic Electronics falls within EPSRC's 'Manufacturing the Future' and 'Non-CMOS Devices' theme. The proposal fits well also with the Welsh Government's economic strategy which includes Advanced Engineering and Manufacturing as one of 4 cornerstones for economic regeneration in Wales and which identifies optoelectronics and advanced materials as cross-cutting themes, all priority areas for financial support through the A4B programme as exemplified by the >£200K support to Taylor's group for a nitrogen glovebox with integrated organic/metal evaporator and spincoater. The group's expertise is already contributing significantly to technology transfer activities by supporting the growth of SMEs such as SmartKem Ltd, a North Wales based company developing high-performance, organic semiconducting materials for the Plastic Electronics industry. The project outomes will therefore contribute directly to the success of these long term investments by developing a new class of organic electronic device with signal processing, electronic memory and optical sensing properties that are compatible with both solution and vacuum processing routes to manufacture. There is also a potential for contributing to EPSRC's Health Technology theme, e.g. potential for fabricating conformal imaging systems for diagnostic applications.
The UK has an excellent track record in both academia and industry for producing high performance materials for Plastic Electronics. The UK printing industry is highly competitive both in the manufacture of printing equipment, e.g. General Vacuum, and as end users, e.g. Camvac (both are represented on the advisory board of our collaborative IeMRC Flagship project:Roll-to-roll Vacuum-based Carbon Based Electronics-RoVaCBE). By extending our expertise from single devices to the design and fabrication of functional systems which requires high reliability and reproducibility, methods of producing interconnects and cross-overs compatible with manufacturing processes, the programme will firmly establish Bangor as a key player in the supply chain between materials producers and end-users.
Beneficiaries of the proposed programme will be UK companies engaged in producing Plastic Electronic products e.g. CDT, Plastic Logic by providing new product opportunities based on CCD principles including imaging systems, signal processing, shift registers, electrically-addressable memory. Excluding OLED and OPV research, virtually all other academic research in Plastic Electronics focuses on the properties of single devices, thus neglecting the problems associated with circuit design and circuit integration and the need for high device yields. The proposed programme will contribute therefore towards filling a gap in the expertise of the UK Plastics Electronics community in these areas and will complement the research being undertaken in our IeMRC project. Chemical companies in the supply chain should also benefit by stimulating R&D into new materials capable of delivering higher performance CCDs. This in turn will feed into better performing transistor materials